Method for the quantitative determination of the dynamic seating comfort of a seat padding

ABSTRACT

A method for determining an evaluation number which is representative of the quality of the dynamic sitting comfort of upholstered seat elements of a vehicle seat. A flexible measuring mat is applied to the upholstered seat element in a defined position and a matrix, which covers the surface, of force measuring sensors which operate without hysteresis is integrated into said measuring mat. A test person or a test body which behaves anthropomorphically in terms of oscillation is positioned on the vehicle seat. In order to carry out a measurement, this body/seat system is excited so as to oscillate, for example by traveling over a bad stretch of road. The signals supplied by the force measuring sensors are added with the same phase to form a composite signal. The frequency response of the body/seat system is determined from this composite signal.

This application claims the priority of German Patent Document No. 10148 662.6, filed 2 Oct. 2001 and PCT/EP02/09302 filed 21 Aug. 2002 thedisclosure of which is expressly incorporated by reference herein,respectively.

The invention relates to a method for quantitively determining thedynamic sitting comfort of upholstered seat elements.

When developing seats, in particular vehicle seats, one of the importantfactors is to achieve a high degree of sitting comfort because thevehicle occupants, especially the driver, must, precisely in the case ofvehicle seats, in some cases stay seated for many hours with littlemovement. In such a situation, questions of optimum seat pressuredistribution, among other things, play a significant role. The behaviorof a seat is determined by a plurality of factors, as for example bytype, design and fabrication of the multilayer composite structure ofthe covering material as well as the material, type and design of thesupport structure of the seat, and by other similar factors. If theseated pressure of an upholstered seat element is distributedunfavorably it will be unpleasant and uncomfortable if the person isseated for a relatively long time.

In the course of the development of a seat, different designs of theseat and of the upholstered elements are produced as trial samples whichmust be compared with one another objectively and in a reproduciblefashion with respect to different testing and evaluation criteria andalso with respect to the pressure comfort so that the best trial samplecan then be selected. Not only new trial samples of a currentdevelopment of a seat but also different test seats from a differentprovenance, for example seats from earlier generations of seats, usedseats or seats from outside development or fabrication workshops arecompared with one another.

According to a known method disclosed in German Patent Document DE 19601 974 C2 (referred to below for short by [2]) for quantitivelydetermining the sitting comfort of upholstered seat elements, thedistribution of the sitting pressure is measured statically between atest ram of anthropomorphic design and the upholstered seat element tobe tested. A thin and flexurally weak measuring mat with a plurality ofseparate pressure sensors integrated into the measuring mat, distributedin the manner of a grid so as to cover the surface and are alsoinherently flexible, are placed between the upholstered surface and thetest ram. The signal outputs of the pressure sensors are connected to anevaluation device. While the sitting surface of the upholstered seat tobe tested is loaded statically, under realistic conditions, by a forcecorresponding to the sitting weight of an average person, the signals ofthe individual pressure sensors of the measuring mat are evaluated andan evaluation number of the pressure comfort of the upholstered elementis determined therefrom according to a specific computational rule. Whenthe comfort evaluation number is determined, different, anthropomorphicsensation areas and different sensation thresholds are taken intoaccount. The known method does in fact provide objective andreproducible evaluation numbers of the sitting comfort for differentupholstered seat elements, which also correlate to the subjectivecomfort sensation of a plurality of test persons.

However, it has become apparent that this statically acquired comfortevaluation number is not representative of the dynamic sitting comfortof a seat. That is to say a seat which has good evaluation with respectto the static sitting comfort does not necessarily also have to be feltto have an optimum degree of comfort when subjected to dynamic seatloading, for example when traveling with the respective vehicle over badstretches of road. The assessment of an upholstered seat element whensubjected to dynamic seat loading is clearly defined by completelydifferent criteria than testing of the comfort of upholstered seatelements in the case of static sitting.

The seat loading body disclosed in German Patent Document DE 197 20 854C1 (referred to below as [1]) and the seat loading body according toGerman Patent Document DE 198 07 751 C1 which is developed further interms of technical oscillation considerations (referred to below as [3])deal with the particular problems of the testing of the comfort ofupholstered seat elements in terms of dynamic criteria. The seat loadingbody according to [1] which is also of anthropomorphic design is freelymovable and corresponds to the sitting weight of an average person. Inorder to obtain the necessary sitting weight of the seat loading body, apassive ballast in the form of a plurality of weights is attached on theinside of the posterior simulator and/or to the back simulator. Theintention is that the freely movable seat loading body will be used tomeasure oscillations, independently of persons, on vehicle seats, whichare comparable at least qualitatively with corresponding test personmeasurements in the overall spectral range from 0 to approximately 30Hz. Similarly to the seat test ram described above for staticexaminations of seats, in the case of the freely movable seat loadingbody, the posterior simulator and the back simulator are also eachformed by hard parts which are covered with upholstery, the lattersimulating, at least on the underside and at the rear, the humanskeleton in a way which is realistic. The coverage of the hard partswith upholstery simulates anthropomorphically, according to thethickness of layers, softness, elasticity and damping behavior as wellas local distribution of these parameters, the soft parts in theposterior area or back area. Thus the coupling of the seat loading body,in terms of technical oscillation considerations, to the upholsteredseat element and upholstered back rest element simulates as precisely aspossible the corresponding junction point between the person and theupholstered elements. This is considered, according to [1], thepredominant precondition in a representative measurement of oscillation,it also being assumed to be important that the seat loading body bringsabout not only a deformation of the surface of the upholstered elementwhich corresponds to a natural person sitting on it, but also adistribution of the sitting pressure which corresponds to a naturalperson sitting on it. Intrinsic dynamic influences of individual bodyparts or body areas are considered, according to [1], to be secondary incomparison with coupling of the seat loading area to the upholsteredelements of the vehicle seat in a way which is close to reality in termsof technical oscillation considerations, i.e. is anthropomorphically“soft”.

So that dynamic influences of the inherently oscillating body mass canbe simulated under conditions close to reality during examinations ofvehicle seats with respect to technical oscillation considerations, andcan be registered as a result, in the further-developed seat loadingbody according to [3] the integrated ballast weights are constructed inthe form of spring/damper/mass systems which are capable of oscillatingin three dimensions. In each case, at least one oscillatory mass issurrounded by a spring/damper medium in such a way that the mass cannotoscillate in all three spatial directions.

The seat loading body according to [1] and [3] have the following incommon: the simulation of the back is mounted so as to be capable ofpivoting about the hip joint within a limited angular space relative tothe posterior simulator, and is prestressed elastically in the sense ofan extended position of the back part and posterior part. The thighsimulators of the posterior part are formed as far as the knee joint,lower leg simulators and foot simulators being connected in a movablefashion in the knee joint area and being able to support themselvesmovably on the floor. The weights of the passive ballast are distributedwithin the seat loading body in such a way that the overall supportingforce in the contact surface of the posterior part and upholstered seatelement and the local distribution of the sitting pressure correspondsto the supporting force and the distribution of sitting pressure when anatural test person is seated. Additionally an approximately identicalposition of the centre of gravity and/or an approximately equally largemoment of mass inertia is produced at least about an axis which isparallel with the hip joint.

In order to carry out seat examinations with respect to technicaloscillation considerations, the vehicle seat which is to be tested isattached, according to [1], on an oscillation platform which can beexcited so as to experience vertical sinusoidal oscillations in thefrequency range of 0-30 Hz. The seat loading body is then placed on thevehicle seat with optimum distribution of the sitting pressure, andlow-mass acceleration sensors are positioned between the sitting surfaceand the seat loading body which is placed in the optimum sittingposition. When the seat is excited so as to oscillate using theplaced-on seat loading body with a defined frequency and definedacceleration amplitude, the response oscillation of the oscillationsystem which is formed from the seat and seat loading body to be testedcan then be determined for each individual excitation oscillation orexcitation frequency using the inserted acceleration sensors. In such anexamination of a vehicle seat with respect to technical oscillationconsiderations, the spectral distribution of the vertical oscillationsof the seat loading body are determined. The frequency response of thevehicle seat is, at it were, determined as a spectral diagram line underloading by the seat loading body. This line represents only theoscillation-damping behavior of a vehicle seat in its entirety withrespect to a person sitting on it. Although this is a usable criterionfor the evaluation of dynamic comfort properties of vehicle seats, theglobal damping behavior of the seat as a whole cannot be used toevaluate the more or less unpleasant oscillation sensation of a personwho is sitting on a dynamically excited vehicle seat.

The object of the invention is to specify a method which, when thecomfort of vehicle seats is examined, provides a quantitive,reproducible evaluation number, under conditions close to reality, whichrelates to the more or less unpleasant oscillation sensation of a humanwho is sitting on a dynamically excited vehicle seat. The dynamicoscillation excitation of the vehicle seat corresponds to the dynamicseat loading, for example when traveling with the respective vehicleover a bad stretch of road.

According to the present invention the entire sitting force of the seatloading body on the upholstered seat element is determined as anintegral of the distribution of the sitting pressure in the frequencyrange of 0-30 Hz which is of interest here, without inertia for eachpoint in time of the response oscillation of the system which is capableof oscillating. When the data are evaluated, the frequency response ofthe system which is capable of oscillating, i.e. the spectraldistribution of the oscillation amplitudes of the response oscillation,is firstly determined, and the integral of this function up to aspecific maximum frequency, for example 20 Hz or 25 Hz, is formedtherefrom, this integral value being used as an evaluation number of thedynamic sitting comfort of the upholstered seat element. This evaluationnumber represents the oscillation loading of the sitting area of thehuman body when it sits on a vehicle seat which is excited so as tooscillate. If the aforesaid integral value of the frequency responsecurve is large, this means a large degree of oscillation loading of thehuman body by the respective vehicle seat, i.e. this seat is felt to beuncomfortable over time. On the other hand, vehicle seats with a lowintegral value are felt to be more pleasant when traveling on badstretches of road.

While the method which is known from publication [1] or publication [3]for carrying out examinations of seats with respect to technicaloscillation considerations reveals the damping property of theupholstered seat element for oscillations, i.e. a property which can beattributed to the upholstered seat element in isolation, the methodaccording to the present invention makes possible an evaluation whichrelates to the interaction between a person and the upholstered seatelement and which corresponds to the sensation of the person in responseto excited seat oscillations.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained below by means of an exemplary embodimentwhich is illustrated in the drawing, in which:

FIG. 1 shows a body, which is placed on a vehicle seat and is ofanthropomorphic design in the posterior area and back area and has fulllower limb dimensions in order to permit the thigh simulators to besupported on the floor, as well as a flexible measuring mat which isapplied in the sitting area,

FIG. 2 shows the grid division of the flexible measuring mat and theindication of the selected force measuring sensors,

FIG. 3 shows, in a highly schematic fashion, the measuring setup duringa measuring journey on a bad stretch of road,

FIGS. 4 a, 4 b and 4 c show the measuring record of the time profile ofthe seat loading for a hard vehicle seat (FIG. 4 a), a normal vehicleseat (FIG. 4 b) and for a soft vehicle seat (FIG. 4 c), obtained duringa measuring journey

FIG. 5 shows the diagrams of a Fourier frequency transformation (FFT) ofthe three profiles according to FIGS. 4 a, 4 b and 4 c, and

FIG. 6 shows the integral functions of the three FFT diagrams accordingto FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The method for determining an evaluation for the quality of the dynamicsitting comfort of upholstered seat elements 2, 3 of a road vehicle 25can be carried out in various ways within the scope of the invention. Inall cases, the vehicle seat 1 to be tested must be loaded underconditions close to reality and excited so as to oscillate. There are anumber of possibilities in terms of the loading, but even more in termsof the excitation so as to oscillate.

The loading of the vehicle seat 1 to be tested can be carried out by atest person or by a test body 15 which is of anthropomorphic design withrespect to sitting. The loading by a test person has the advantage thatsuch a test person is almost always readily available, in particularwithout previous investment. However, the use of test persons has thedisadvantage that the tests cannot always be carried out with the sametest person and as a result the measurement results are not readilycomparable with one another. For this reason, the loading of the vehicleseat to be tested with a test body of anthropomorphic design is to berecommended despite the investment which is necessary.

In particular concerning the excitation of oscillations of the body/seatsystem which is formed in this way and is capable of oscillating, thereare different possibilities in this respect. Specifically, the systemwhich is capable of oscillating and is formed from the seat loading bodyand vehicle seat can be excited in isolation in order to make itoscillate, for example on an oscillation test stand for vehicle seats orin the installed state in the respective vehicle 25. The latteralternative is preferably recommended since the intrinsic oscillationbehavior of the vehicle is then in fact included in the result of themeasurement of oscillations. The same vehicle seat, which gives rise togood measurement results when there are oscillation measurements in onetype of vehicle, i.e. was evaluated as a very comfortable seat in termsof oscillation in this type of vehicle, is not required to produce anequally good comfort evaluation when tested in another type of vehicle.The excitation of the vehicle so as to oscillate can itself be carriedout under conditions close to reality in such an examination bytraveling over a bad stretch of road or on what is referred to as ashaking test bench in which each of the four wheel hubs of the vehicleare attached to one shaker each, and the four shakers are excited, in aprogram-controlled fashion and with assigned phase, so as to oscillateunder conditions close to reality in accordance with traveling over abad stretch of road. Traveling over a bad stretch of road does notrequire the investment in an expensive vehicle shaking test stand. Onthe other hand, a precondition for excitation of oscillating bytraveling over a bad stretch of road is that the test journey can alwaysbe carried out over the same road and the same stretch on it and alwaysunder the same travel conditions such as state of the road (dry), speed(constant, approximately 60 km/h), straight-ahead travel, which is undercertain circumstances possible only with certain restrictions. Inaddition, an oscillation test of vehicle seats at different developmentlocations by traveling over a bad stretch of road which is respectivelyavailable locally, i.e. different bad stretches of road, may lead undercertain circumstances to slightly different measurement results. In anycase, excitation of oscillating by traveling over a bad stretch of roadis problematic if the same vehicle seat is to be tested by differentdevelopment teams which operate far apart from one another in terms oflocation. In such a case, it is instead recommended to carry outexcitation of oscillating in each case by means of a vehicle shakingtest stand which can be provided with the same excitation program atboth locations.

When the vehicle seat is examined with respect to oscillation, thesystem which is capable of oscillating and is formed from the seatloading body and vehicle seat can, as stated, also be excited tooscillate in the desired spectrum by means of a seat test stand. Thisexcitation possibility is advantageous in that the investmentexpenditure on such a test stand is relatively low in comparison with avehicle shaking test stand. In addition, oscillation of the vehicle seatwith respect to oscillation is carried out in a building, independentlyof the weather, and always under the same conditions. There are in turnvarious possibilities for excitation of oscillating by means of a seattest stand.

Specifically, the body/seat system can be excited by means of sinusoidaloscillations, the excitation frequency changing slowly, i.e.quasi-statically and being adjusted through the desired spectrum from 0to 30 Hz. The amplitudes of the response oscillation which arerespectively set to the excitation of oscillating are recorded at thesame time as a function of the excitation frequency. Thisamplitude/frequency record constitutes the frequency response of thebody/seat system which is capable of oscillating.

On the other hand, the body/seat system can be excited by the seat teststand using a stochastic mixture of oscillations which changes overtime. The stochastic excitation oscillation was measured in advance on ameasuring journey over a bad stretch of road. The stochastic excitationof the body/seat system must be maintained for a certain time and thelikewise stochastic response oscillation of the system must be recorded.By means of a Fourier frequency transformation, the frequency responseof the body/seat system which is capable of oscillating, and which is ofinterest here, is determined from the time profile from the responseoscillation.

In the exemplary embodiment illustrated in FIG. 1, the vehicle seat 1 isloaded during the examination with respect to oscillation by means of afreely movable test body 15 of anthropomorphic design which, with theintermediate positioning of a measuring mat 6 which is applied to theupholstered seat element 2 in a defined position, is itself also placedon the upholstered seat element in a defined position and rested againstthe upholstered back rest element 3.

The test body 15 is composed of a thigh and posterior area 16 which iscovered with upholstery, of a back area 17 which is connected in anarticulated fashion thereto at the hip joint and is also covered withupholstery, and of a pair of lower leg simulators 19 which are connectedto the thigh simulators in the knee joint area 20 in an articulatedfashion and are supported on the floor by means of footplates 22 whichare connected in an articulated fashion 21. The hard parts of the thighand posterior area 16 and those of the back area 17 realisticallysimulate, at least on the underside and the bearing side, the shape ofthe pelvic bone and of the thighs including the thigh joints of a humanskeleton. The coverage of the hard parts with upholstery simulates, asrealistically as possible, the natural soft parts in the posterior areaand back area in terms of the layer thickness, softness, elasticity anddamping behavior as well as local distribution of these parameters, inparticular in the area of the two sitting pressure points. In addition,in order to obtain the necessary sitting weight, the test body 15 whichis of anthropomorphic design is provided with a plurality of ballastweights 18 which are attached to the thigh and posterior area 16 and/orare secured on the inside of the back area 17.

The test body is expediently configured in terms of its proportions andits weight in such a way that it corresponds to the average of all malepersons, i.e. a 50 percentile man. Women do have different proportionsin the posterior area from men so that it may appear advantageous tocarry out measurements with a female 50 percentile test body in additionto the measurements with a male 50 percentile test body. The differencesare, however, less significant in comparison with the differencesbetween a 50 percentile man and a very large 95 percentile man or withrespect to a very small 5 percentile man. Comparative measurements witha male and a female 50 percentile test body would therefore presumablyonly reveal marginal differences in the measurement result, which wouldprobably not, at least not to a significant extent, lie outside thenormal measuring inaccuracy or measuring variation. At any rate, itcould be expedient to make the measurement result somewhat more reliableby carrying out multiple measurements using a male and a female 50percentile test body and forming a mean value from the final values ofthe individual measurements. Such safeguarding of the measured valuescould also be extended as desired by multiple measurements not only ofmale and female 50 percentile test bodies but also with 5 percentiletest bodies and 95 percentile test bodies, respectively male and female,and by a subsequent formation of mean values.

The flexible measuring mat 6 which is necessary to examine the vehicleseat with respect to oscillation and is applied to the upholstered seatelement of the vehicle seat in a defined position is provided with aplurality of separate force measuring sensors 8 which are each alsoinherently more flexible. The force measuring sensors which areintegrated into the measuring mat are grid-like and distributed in it tocover the surface. In the exemplary embodiment illustrated in FIG. 2,the force measuring sensors 6, which are square in terms of the surfacethey require, are indicated by a checker-board-like line grid; alongeach side of the measuring mat. In each case 32 fields are provided sothat the measuring mat contains 32×32=1024 force measuring sensors. Inorder for the measuring mat to be suitable for investigations ofoscillation it is a precondition that the force measuring sensors eachoperate virtually without hysteresis up to a frequency of approximately25 Hz. The force measuring sensors operate according to the capacitiveprinciple. The opposite poles of each sensor are each provided with asignal terminal which leads outside to the evaluation device. However,each individual force measuring sensor does not need to be provided witha separate pair of line terminals. Instead it is sufficient if the polesof the force measuring sensors which lie on the one side of the mat areconnected to one another in rows by a first set of lines, and the poleswhich lie on the opposite side of the mat are connected to one anotherin columns by a second set of lines, and this total of 2×32=64 lines arelead outwards in an insulated fashion in a corresponding four-conductorconnecting cable 9. Each individual force sensor can be addressedindependently by different pairing of the first and second lines.

The signal outputs of the force measuring sensors must be sampled with asampling frequency of approximately 100 Hz in order to acquiresufficient measuring points within an oscillation cycle even at therelatively high frequencies of the response oscillation which are ofinterest. It is not necessary to evaluate the measuring signals of allthe 1024 force measuring sensors of the measuring mat. Given the currentstate of computer technology and with the aforesaid sampling frequencythis would result in unacceptably high demands being made of theevaluation unit with respect to computing capacity and computing speed.Instead, an appropriate local selection of force measuring sensors hasreduced the number thereof to approximately 70 to 90 items, that is tosay to a degree which can already be readily processed today by means ofmobile computers (laptops) given the aforesaid sampling frequency. Inthe exemplary embodiment shown in FIG. 2, 76 sensors 8′ of the measuringmat are active.

It is conceivable to have a uniform distribution of the selected“active” force measuring sensors over the measuring mat, which alsoproduces usable measuring results. However, the measurements are clearerif the selected force measuring sensors 8′ are concentrated in themainly loaded areas, and here in turn in the ischial tuberosity area 10.Given a satisfactory arrangement of the measuring mat on the vehicleseat and of the test body on the measuring mat, the load fields extendsymmetrically with respect to the center line 7 of the measuring mat.Here, in addition to the two ischial tuberosity areas 10, which take upthe main load, there are also two side cheek areas 12 and two lower legareas as well as a coccyx area. The seat edge area 11 indicated in FIG.2 constitutes the front part of the lower leg area.

After the vehicle seat 1 has been installed satisfactorily in therespective road vehicle 25 (FIG. 3) and has been prepared with themeasuring mat 6 and after the anthropomorphic test body 15 has beencorrectly positioned on it and secured on the upholstered back restelement 3 by means of a seat belt, the signal terminals of the forcemeasuring sensors 8′ (connecting cables 9) are connected to theevaluation unit. In the exemplary embodiment illustrated in FIG. 3, theevaluation unit is composed essentially of a computer 27, an FFTanalyzer 28, an integrator 29 and an end display 30. Before themeasurement, it is necessary to check once more whether the test body 15is seated correctly, which can be done by checking the static weightdisplay before excitation of oscillating. To be specific, the actualoverall force of all the selected force measuring sensors 8′ mustcoincide to a set point overall force which is determined in advance forthe seat loading body used. If appropriate, the sitting position of theseat loading body on the vehicle seat 1 must be corrected until a setpoint/actual correspondence is obtained. If a natural test person isused as the seat loading body, the measurement must also not be starteduntil the measuring mat has assumed body heat, which is the case at theearliest after approximately 5 to 7 minutes.

In the exemplary embodiment illustrated in FIG. 3, in order to carry outa measurement the body/seat system is excited to oscillatestochastically by traveling with the vehicle 25 over a bad stretch 26 ofroad so that excitation oscillations within the frequency range of 0 to30 Hz which are of interest here are also included. The signals whichare present at the force measuring sensors during the excitation timeare evaluated in real time in the aforesaid evaluation unit 27-30. It isalso conceivable instead to record merely the time profile of theindividual signals and later carry out the evaluation offline in alaboratory where more computing time is available.

The measuring journey on the bad stretch 26 of road is to be carried outunder the same conditions for all the measurements, specificallystraight-ahead travel with constant speed of approximately 50 to 60 km/hon a dry underlying surface. The measuring travel is carried out over ameasuring time of at least approximately 5 minutes. If a straightstretch of bad road of approximately five km in length is not available,a shorter part of a straight bad stretch 26 of road is traveled alongbackward and forward repeatedly, the measuring signals and theirprocessing being suppressed during the turning maneuver.

When the measuring signals are processed, the signals of all the forcemeasuring sensors 8 are in all cases added at least approximately withthe same phase to form a composite signal 31, which takes place in thecomputer 27. FIGS. 4 a, 4 b and 4 c each show a force profile which hasbeen recorded on a hard vehicle seat (FIG. 4 a; composite signal 31 h),on a normal vehicle seat (FIG. 4 b; composite signal 31 n) and on a softvehicle seat (FIG. 4 c; composite signal 31 w).

The spectral distribution of the amplitudes of the response oscillationof the body/seat system, referred to as the frequency response 32, isdetermined from the time profile of this composite signal 31 by means ofthe FFT analyzer 28. The various frequency responses 32 h, 32 n and 32 wof the hard vehicle seat, of the normal vehicle seat and of the softvehicle seat are illustrated in a direct comparison in FIG. 5. Althoughthe differences are not yet very striking, their tendency isrecognizable despite certain systematic correspondences of the frequencyresponses, for example with respect to the spectral position of theresonant points. The increasing resonance at the resonant point 5 Hz issignificantly greater with a hard seat than with a soft seat or with anormal seat. The tendency of the profile of the frequency response 32 nof the normal seat is at the lowest level overall.

In the integrator 29, the ratio of the area integral 33 of thisfrequency response is determined up to a certain limit frequency 35, thelimit value 34 h, 34 n, 34 w of this ratio of the area integral 33 h, 33n, 33 w at the limit frequency 35, in the example 20 Hz, being used asan evaluation number of the dynamic sitting comfort of the upholsteredelement of the vehicle seat 1. The integral lines 33 h, 33 n and 33 w ofthe hard seat, of the normal seat and of the soft seat (FIG. 6) allowthe differences between the various seats to be recognized more clearlythan the frequency responses according to FIG. 5. In particular, bymeans of the limit value 34 h, 34 n or 34 w it is possible to expressthe oscillation comfort of the respective vehicle seat in a comparableand reproducible fashion merely by a numerical value.

It is an advantage of the invention in comparison with the measuringmethod known from [1] that an easily comparable evaluation number isacquired as a result of the measurement, which number is not onlyrepresentative of the criterion of the seat to be measured but also canbe reproduced during later measurements with only a small degree ofvariation. A further important advantage of the measuring methodaccording to the invention over the prior art is that the inventionactually registers the sensitivity of the human body to seatoscillations using measuring technology, i.e. by means of the acquiredcomfort evaluation number it is possible to obtain quantitive andcomparable definitive information on the oscillation loading on thehuman body by the respective vehicle seat during a relatively longjourney, which was previously impossible.

1-11. (canceled)
 12. A method for determining an evaluation number whichis representative of a quality of the dynamic sitting comfort ofupholstered elements of a vehicle seat, said method comprising thesteps: applying a flexible measuring mat to the upholstered seat elementof the vehicle seat in a defined position, said measuring mat beingprovided with a plurality of separate force measuring sensors which areintegrated into the measuring mat, are distributed in the manner of agrid so as to cover a surface of the mat, are also each inherentlyflexible, are each operate virtually without hysteresis up to afrequency of approximately 25 Hz and are each provided with signalterminals which lead outwards to an evaluation device; subsequentlyloading the vehicle seat with a seat loading body under conditions closeto reality; positioning said seat loading body in a defined position,centrally on the vehicle seat, wherein said seat loading body is one ofa natural test person and a freely movable test body which is designedso as to be anthropomorphic with respect to the oscillatory behavior ofthe vehicle seat; exciting a system formed by the seat and the body soas to oscillate at least within a frequency range of 0 to 30 Hz; atleast one of recording and analyzing signals which are present at signalterminals of the force measuring sensors during the excitation where thesignals of all the force measuring sensors are added at leastapproximately with the same phase to form a composite signal;determining the spectral distribution of the amplitudes of a responseoscillation of the body/seat system from the time profile of saidcomposite signal; and determining a ratio of an area integral of saidfrequency response up to a specific limit frequency; using a limit valueof said ratio of the area integral being used at the limit frequency assaid evaluation number of the dynamic sitting comfort of the upholsteredelement of the vehicle seat.
 13. The method as claimed in claim 12,wherein the freely movable test body is of an anthropomorphic design andcomprises a thigh and posterior area covered with upholstery a back areaconnected at the hip joint in an articulated fashion and is covered withupholstery, and a pair of lower leg simulators connected to the thighsimulators in the knee joint area (20) in an articulated fashion andsupported on the floor by means of footplates which are connected in anarticulated fashion, wherein hard parts of the thigh and posterior areaand the back area simulating as true to nature as possible, at least onthe underside and the bearing side, the shape of the pelvic bone and ofthe thighs including the thigh joints of a human skeleton, and whereinthe coverage of the hard parts with upholstery simulating as true tonature as possible the natural soft parts in the posterior area and backarea in accordance with the layer thickness, softness, elasticity anddamping behavior as well as local distribution of these parameters inthe area of the two sitting pressure points, wherein the freely movabletest body which is of anthropomorphic design is also provided withpassive ballast in the form of a plurality of ballast weights which areat least one of inserted on the inside into the thigh and posterior areaand secured to the inside of the back area in order to obtain thenecessary sitting weight.
 14. The method as claimed in claim 12, whereinthe body/seat system is excited by means of stochastic oscillations, andthe spectral distribution is determined from the composite signal of theresponse oscillation by means of a Fourier frequency transformation. 15.The method as claimed in claim 14, wherein the vehicle seat to beevaluated with respect to its dynamic sitting comfort is installedaccording to predetermined regulations in the vehicle, and wherein thebody/seat system is excited stochastically to oscillate by the wheels ofthe vehicle.
 16. The method as claimed in claim 15, wherein thestochastic excitation of oscillations takes place as a result of thevehicle traveling over a defined road.
 17. The method as claimed inclaim 12, wherein approximately 70 to 100 force measuring sensors areselected from the plurality of force measuring sensors integrated intothe measuring mat and only signals of said selected sensors are furtherprocessed, wherein the selected force measuring sensors being preferablyarranged in an ischial tuberosity area.
 18. The method as claimed inclaim 12, wherein, before the step of exciting the system, a checking iscarried out to determine whether the actual overall force of all theforce measuring sensors corresponds to a set point overall force whichis determined in advance for the seat loading body used, the sittingposition of the seat loading body on the vehicle seat is corrected untila set point/actual correspondence is brought about.
 19. The method asclaimed in claim 12, wherein when a person is used as the seat loadingbody, the measurement of oscillations is not started until the measuringmat has assumed body heat.
 20. The method as claimed in claim 16,wherein a measuring journey on said defined road is carried out withstraight-ahead travel at a constant speed of approximately 50 to 60 km/hon a dry underlying surface.
 21. The method as claimed in claim 20,wherein a measuring journey is carried out over a measuring time of atleast approximately 5 minutes.
 22. The method as claimed in claim 16,wherein if a straight portion of said of road of approximately 5 km inlength is not available, a shorter part of a straight portion of road istraveled over repeatedly backward and forward, the measuring signals andtheir processing being suppressed during a turning maneuver.
 23. Asystem for determining relative quality of dynamic comfort ofupholstered elements of a vehicle seat, said system comprising: aflexible measuring mat applied to an upholstered seat element in adefined position wherein said flexible measuring mat includes aplurality of forced measuring sensor distributed as a grid to cover asurface of the mat, wherein each of said sensors are flexible andoperate without hysteresis to a frequency of approximately 25 Hz andwherein each of said sensors are provided with an output terminal; anevaluation device connected to received output signals from each of saidoutput of said measuring devices; an excitation device for oscillatingsaid seat and said measuring mat within a range of frequency between 0and substantially 30 Hz; a measuring system for measuring and analyzingoutputs of said measuring sensors including means for adding at leastapproximately within the same phase a force measuring sensor output toform a composite signal and performing a spectral distribution ofamplitudes of response oscillations of a system formed by said seat andsaid mat from the time profile of said composite signals; means fordetermining a ratio of an area integral of said frequency response to aspecific limit frequency when a limit value of said ratio of the areaintegral at the limit frequency provides an evaluation number indicatingsaid quality.
 24. The system according to claim 12, further including atest body providing on said flexible mat.